This invention relates to vehicle identification systems, in particular one which permits the non-invasive identification of a vehicle even under adverse environmental condition.
Vehicle identification systems have been developed for a number of purposes. One purpose is to permit law enforcement agencies to quickly check whether a vehicle has been stolen or has forged license plates. One such system is shown in U.S. Pat. No. 4,368,979 to Ruell. This system combines the alphanumeric information carried by a license plate with a hologram including information which cannot be seen by the unaided human eye and also must be decoded to be understandable. Although such a system could be used to identify vehicles, the identifying hologram is limited as to size. Also, the recommended placement of the identifying hologram at or near the rear license plate creates a situation in which the hologram can be obscured by snow, ice and mud, which often accumulates on vehicles, as well as by other vehicles.